asus-me176c: update kernel to 5.4.107, fix splash screen width and phosh scaling

Update linux-asus-me176c to 5.4.107, also fix splash screen width and phosh scaling in device-asus-me176c:

Actually the display in asus-me176c has a width of 800px, which means that the splash screen isn't perfectly centered. Correct this in deviceinfo to make it show up correctly. Also, add configuration file for Phosh to reduce scaling a bit to 1.75. It's kind of subjective but scaling = 2 definitely feels too large.